Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

980
FXUS63 KLOT 300254
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
854 PM CST Thu Jan 29 2026

.KEY MESSAGES...

- Cold conditions will continue into the weekend with mainly
  subzero wind chills through Saturday morning.

- Threat for impactful lake effect snow continues to increase
  for Friday into/through Saturday. After likely accumulations
  and impacts in northeast/eastern IL on Friday, focus shifts
  into primarily northwest Indiana Friday night-Saturday, though
  it could be close for parts of IL.

- Winter Storm Warning in effect for Lake (IN) and Porter (IN)
  counties late Friday into Saturday. A Winter Storm Watch
  remains in effect for central and southern Cook County late
  Friday into Saturday. Advisories in effect for Lake (IL),
  Cook, and Dupage Friday morning through Friday afternoon.

- There may be a period of light snow accumulations Sunday night
  into Monday, followed by less cold conditions by midweek.

&&

.UPDATE...
Issued at 853 PM CST Thu Jan 29 2026

Forecast appears on track with no big changed planned this
evening. Did move the end time of the winter storm watch for
central and southern Cook County to midnight Friday night as
lake effect band will likely shift east into Indiana sometime
Friday evening. While it could shift back west into Illinois
sometime Saturday morning, that would likely be handled with a
separate headline.

Guidance has been trending a bit slower with the arrival of the
lake enhanced surface trough Friday morning. Slowed the timing
of the snow arrival down just a bit Friday morning to trend in
this direction, but it is still well within the advisory timing.
Still looks likely that a band of potentially intense snow will
accompany this trough as it moves inland, with a quick 1-3" of
snow possible in the advisory area, especially the northern
suburbs.

Decided to upgrade Lake and Porter Counties in Indiana to a
winter storm warning, as the probabilities of totals over 6
inches near the lake are very high. Given the likelihood of
mesoscale oscillations in the position of the band, which are
nearly impossible to predict with much lead time, it will be
hard to pin down precisely where the highest snowfall totals
will end up. Should the band end up stationary in one area for
extended period, then isolated totals over a foot would
certainly be possible.

One note caution, for those looking at the somewhat modest QPF
being offered in some of the high resolution models, keep in
mind that snow to liquid ratios will likely end up in the 30:1
range or higher! Given the exceptionally favorable lake effect
snow parameters, seems likely that this band will likely produce
snowfall rates of 2"+ per hour at times Friday night into
Saturday morning.

- Izzi

&&

.DISCUSSION...
Issued at 314 PM CST Thu Jan 29 2026

A prolonged period of intense Lake Effect Snow (LES) continues
to look increasingly likely (80%+ chance) for parts of the area
Friday morning through early Saturday evening. This event will
in two parts, an initial fairly fast-moving wave of intense snow
showers late Friday morning through early/mid afternoon, and
then a prolonged period of LES, likely beginning into parts of
Cook county in NE IL late Friday afternoon/evening, before
focusing primarily across our NW Indiana counties (and
Lake/Porter) late Friday night into Saturday morning, before
potentially sloshing west back towards the NE Illinois shore and
coming to an end late Saturday.


Headlines...

The Winter Storm Watch remain in place across Lake and Porter
counties in IN from late Friday afternoon through Saturday. The
main changes to the headlines was to hoist a Winter Weather
Advisory for Lake IL, Cook and Dupage counties from 9am Friday
morning through 3 pm Friday afternoon to account for the first
burst of snow expected to shift in off the lake. Thereafter, we
have opted to add central and southern Cook county to the Winter
Storm Watch, which will run from 3 PM Friday afternoon through
6 am Saturday morning, for the beginnings of the intense lake
effect band.


Friday Morning through mid Afternoon Snow...

Lake effect snow will initially focus into an intense NNW-SSE
oriented band over eastern portions of Lake Michigan later
tonight as boundary layer convergence ramps-up along an
approaching inverted surface trough shifting south and west out
of western lower Michigan. Then, as we head into Friday morning,
this intense band will be forced west-southwestward into
northeastern IL (and possible parts of far NW IN) as a southward
advancing synoptic scale trough shifts overhead. The primary
timing for this heavy burst of snow will be in the 9 AM to noon
timeframe, before spreading inland into the early to mid
afternoon hours of Friday. There still remains some degree of
uncertainty with how far inland the band of the more intense
snow showers will reach. However, weakening boundary layer
convergence along the inverted surface trough is likely to
result in a weakening trend to the band of snow with inland
extent Friday afternoon.

The band of snow the comes ashore in northeastern IL Friday
morning is expected to be fairly progressive, but at least
briefly intense. Impressive lake induced thermodynamics (lake
induced ELs up to 10,000 ft) will support heavy convective
elements within this band of snow, which is expected to support
snow rates of 1-2" per hour, particularly in close proximately
to the lake. While the residence time of this intense band of
snow will only be up to 2-3 hours at a given location, snow
rates this high could easily add up 2" to 3"+ and result in
adverse travel conditions for a few hours on Friday. It is for
this reason we opted to hoist a Winter Weather Advisory for
areas within close proximately to the lake (Lake IL, Cook and
Dupage) Friday morning and afternoon.


Late Friday afternoon through Saturday Lake Effect Snow...

This is the main period of lake effect snow we continue to be
concerned with. While the latest guidance continues to focus the
main show across NW Indiana late Friday night into Saturday,
there are increasing concerns that the redeveloping intense lake
effect snow band could impact portions of central and eastern
Cook near the lake late Friday afternoon into the evening. The
band may remain somewhat transient here, which could in turn
limit the residence time of heavy snow rates. However, even a
few hour period of snow rates of 2-3"+ could support isolated
areas of 6"+ across parts of Chicago and the southern suburbs in
southern Cook, we felt it worth while to include them in the
Winter Storm Watch.

There continues to be a strong agreement amongst forecast
guidance that strong northwesterly winds on the west side of the
lake will act to drive the main focus for this intense lake
effect band eastward into Lake and Porter counties in
northwestern IN either late Friday evening or Friday night.
Thereafter, the band of lake effect may oscillate back and forth
a bit across parts of Lake and Porter counties as additional
meso-lows shift southward down the lake and reorient the main
band. It also remains plausible that some of the more intense
snow showers could work back close to the Cook county shore for
a period on Saturday. We will have to keep a close eye on this.
Lake thermodynamics will be in the waning stages Saturday
afternoon, so while embedded heavier rates will remain, overall
breadth and intensity of LES is expected to be on a downward
trend through Saturday afternoon before ending entirely into the
evening.

While confidence is high in the occurrence of this intense and
impactful lake effect band of snow Friday night into Saturday
(1-2" per hour snow rates, which could easily support double
digit totals), lingering uncertainties in the movement and exact
placement of the band has kept us from transitioning any of the
watch to a warning for the time being.


Sunday and Beyond...

Active northwest flow will continue beyond this weekend`s
system and into next week, and will guide several disturbances
across the general region through next week. Medium range
guidance continues to resolve the first of these waves scooting
across the Upper Midwest and Great Lakes region sometime during
the Sunday PM - Monday timeframe. In general, large scale height
falls don`t appear all that impressive, with the main surface
trough and associated low forecast to slide well to our north.
However. fairly robust DCVA on the southern flanks of this
feature, coupled with north-south transient bands of mid-level
f-gen may be sufficient to crank out some light snowfall over
parts of the area, particularly the closer to the Wisconsin
state line you get. The fairly quick forward progression of this
system, as well as a general lack of deeper moisture, suggests
snowfall amounts will be light, probably limited to a few tenths
to an an inch or so. Based on the latest guidance trends, it`s
possible dry air plays a role and ultimately limits snowfall
chances with this feature as well.

Deterministic and ensemble guidance spread increases markedly
after Tuesday, lowering overall forecast confidence during the
middle and end of next week. With a lingering baroclinic zone
just to our south, there`s a potential for some continued
precipitation chances even into Tuesday/Wednesday, but this is
far from ubiquitous across the guidance suite.

While below normal temperatures are expected to continue into
early next week, there` a decent model signal for at least a
moderating trend during the middle and end of the week, with
highs potentially pushing near and above freezing.


KJB/Carlaw

&&

.AVIATION /00Z TAFS THROUGH 06Z SATURDAY/...
Issued at 552 PM CST Thu Jan 29 2026

- Wind shift from light NW to gusty northeast expected mid-late
  morning Friday

- Lake-enhanced convective snow showers are likely along and
  behind the front wind shift/cold front, highest coverage and
  intensity expected closer to the lake.

- Additional lake effect snow showers possible in the afternoon
  at ORD/MDW/GYY.

Challenging, lower confidence forecast Friday due to the
typically challenging nature of lake effect snow showers. We`re
expecting pretty robust band of snow showers to accompany a cold
front across the terminals mid-late morning Friday, hitting
ORD/MDW first, then likely spreading inland to DPA, and possibly
as far west of RFD, though confidence decreases as far west as
RFD. There is still considerable spread in guidance in the
timing of the wind shift to northeast and the corresponding
onset of the snow showers. Opted to stick close to the timing of
the previous TAFs, but worth noting that it could be an hour or
so earlier or later than the timing in the 00z TAFs. By the 09z
TAFs, there will hopefully be greater confidence on timing of
the wind shift/snow onset timing.

Additional lake effect snow showers will remain possible through
the afternoon Friday, with the highest chances at ORD, MDW, and
GYY. Opted to stick with just a PROB30 for now as confidence is
still low on if the Chicago terminals get hit with afternoon
lake effect snow showers and if so, when it may happen.

- Izzi

&&

.HYDROLOGY...
Issued at 230 PM CST Wed Jan 28 2026

River gauges, reports from local officials, and reports from
trained ice spotters continue to indicate a few ice jams across
the area due to the significant increase in river ice over
recent days. With continued cold weather into next week,
conditions will remain favorable for river ice formation. While
no widespread flooding is expected, localized ice jams may
occur.

- NWS Chicago

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Winter Weather Advisory from 9 AM to 3 PM CST Friday for
     ILZ006-ILZ013-ILZ103-ILZ104-ILZ105.

     Winter Storm Watch from Friday afternoon through Friday
     evening for ILZ104-ILZ105.

IN...Winter Storm Warning from 3 PM Friday to 6 PM CST Saturday for
     INZ001-INZ002.

LM...Small Craft Advisory from 9 AM Friday to 6 PM CST Saturday for
     Winthrop Harbor IL to Gary IN.

     Small Craft Advisory from 3 PM Friday to 3 AM CST Sunday for
     Gary to Burns Harbor IN-Burns Harbor to Michigan City IN.

&&

$$

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